4654 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 23
Sun et al.
9.2 Hz; H-3), 4.60, 4.69 (1H each, both br s; H2-29). Anal.
(C38H62O8‚1/2H2O) C, H.
m; H-19, H2-2′, H2-4′), 3.20 (1H, dd, J ) 5.2, 10.9 Hz; H-3),
3.87, 4.29 (1H each, both d, J ) 11.1 Hz; H2-28), 4.60, 4.70
(1H each, both s; H2-29). Anal. (C37H60O5‚1/2H2O) C, H.
28-O-(3′,3′-Tetr a m eth ylen eglu ta r yl)-betu lin (23): yield
68% (a fter ch r om a togr a p h y w ith n -hexane/acetone [6:1]),
3,28-Di-O-glu ta r yl-d ih yd r obetu lin (16): yield 68% (after
chromatography with n-hexane/EtOAc [3:1]), an amorphous
powder; [R]25D -10.0 (c ) 0.68, CHCl3); 1H NMR (CDCl3) δ 0.75,
0.82 (3H each, both d, J ) 6.6 Hz; 20-(CH3)2), 0.82 (6H), 0.84,
0.93, 1.02 (3H each, except 0.82, all s; 4-(CH3)2, 8-CH3, 10-
CH3, 14-CH3), 1.90-2.00 (4H, m; H2-3′, 3′′), 2.35-2.44 (8H,
m; H2-2′, 2′′, 4′, 4′′), 3.81, 4.26 (1H each, both d, J ) 11.1 Hz;
H2-28), 4.47 (1H, dd, J ) 5.3, 10.4 Hz; H-3). Anal. (C40H64O8‚
1/2H2O) C, H.
recovered betulin 20%, an off-white amorphous powder; [R]25
D
+13.4 (c ) 0.5, CHCl3); 1H NMR (CDCl3) δ 0.77, 0.83, 0.98
(6H), 1.04 (3H each, except 0.98, all s; 4-(CH3)2, 8-CH3, 10-
CH3, 14-CH3), 1.69 (3H, s; 20-CH3), 2.45 (1H, dt, J ) 5.6, 10.7
Hz; H-19), 2.58 (4H, s; H2-2′, H2-4′), 3.20 (1H, dd, J ) 5.1, 10.8
Hz; H-3), 3.88, 4.30 (1H each, both d, J ) 11.0 Hz; H2-28),
4.60, 4.70 (1H each, both s; H2-29). Anal. (C39H62O5‚1/2H2O)
C, H.
3,28-Di-O-(RS-3′-m eth ylglu ta r yl)-d ih yd r obetu lin (17):
yield 72% (after chromatography with n-hexane/acetone [8:1]),
1
an amorphous powder; [R]25 -6.3 (c ) 0.5, CHCl3); H NMR
3-Deoxy-2,3-d ih yd r o-28-O-(3′,3′-d im eth ylglu ta r yl)-bet-
u lin (39): yield 53% (after chromatography with n-hexane/
D
(CDCl3) δ 0.75, 0.82 (3H each, both d, J ) 6.6 Hz; 20-(CH3)2),
0.83 (6H), 0.84, 0.93, 1.03 (3H each, except 0.83, all s; 4-(CH3)2,
8-CH3, 10-CH3, 14-CH3), 1.04 (6H, d, J ) 7.0 Hz; 3′-CH3, 3′′-
CH3), 2.22-2.49 (10H, m; H2-2′, 2′′, 4′, 4′′, H-3′, H-3′′), 3.80,
4.27 (1H each, both d, J ) 11.0 Hz; H2-28), 4.48 (1H, dd, J )
5.3, 10.4 Hz; H-3). Anal. (C42H68O8) C, H.
acetone [10:1]), an off-white amorphous powder; [R]25 +26.4
D
(c ) 0.49, CHCl3); 1H NMR (CDCl3) δ 0.84, 0.85, 0.92, 0.97,
1.04 (3H each, all s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 1.13
(6H, s, 3′-(CH3)2), 1.67 (3H, s, 20-CH3), 2.38-2.48 (1H, m;
H-19), 2.45, 2.45 (each 2H, both s; H2-2′, H2-4′), 3.86, 4.28 (1H
each, both d, J ) 11.1 Hz; H2-28), 4.58, 4.67 (1H each, both br
s; H2-29), 5.34-5.37 (2H, m; H-2, H-3). Anal. (C37H60O4) C,
H.
3,28-Di-O-(3′,3′-d im eth ylglu ta r yl)-d ih yd r obetu lin (18):
yield 81% (after chromatography with CHCl3/acetone [19:1]),
an amorphous powder; [R]25D -15.0 (c ) 0.2, CHCl3); 1H NMR
(CDCl3) δ 0.77, 0.84 (3H each, both d, J ) 6.7 Hz; 20-(CH3)2),
0.85, 0.86 (6H), 0.95, 1.04 (3H each, except 0.86, all s; 4-(CH3)2,
8-CH3, 10-CH3, 14-CH3), 1.14 (12H, s; 3′-(CH3)2, 3′′-(CH3)2),
2.43-2.54 (8H, m; H2-2′, 2′′, 4′, 4′′), 3.83, 4.29 (1H each, both
d, J ) 11.0 Hz; H2-28), 4.52 (1H, dd, J ) 4.8, 11.0 Hz; H-3).
Anal. (C44H72O8) C, H.
3-Deoxy-2,3-dih ydr o-28-O-(3′,3′-tetr am eth ylen eglu tar yl)-
betu lin (40): yield 77% (after chromatography with n-hexane/
acetone [22:1]), an off-white amorphous powder; [R]25 +25.7
D
(c ) 0.50, CHCl3); 1H NMR (CDCl3) δ 0.85, 0.86, 0.93, 0.97,
1.05 (3H each, all s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 1.67
(3H, s, 20-CH3), 2.43 (1H, dt, J ) 5.2, 11.0 Hz; H-19), 2.55
(4H, s; H2-2′, H2-4′), 3.88, 4.29 (1H each, both d, J ) 11.1 Hz;
H2-28), 4.58, 4.68 (1H each, both br s; H2-29), 5.32-5.42 (2H,
m; H-2, H-3). Anal. (C39H62O4) C, H.
3,28-Di-O-(RS-3′,3′-m eth yleth ylglu ta r yl)-d ih yd r obetu -
lin (19): yield 84% (after chromatography with n-hexane/
EtOAc [6:1]), an off-white amorphous powder; [R]25 -17.6 (c
D
1
) 0.49, CHCl3); H NMR (CDCl3) δ 0.78, 0.85 (3H each, both
3,28-Di-O-a cetyl-betu lin (24). A solution of betulin (1.926
g, 4.35 mmol) in anhydrous pyridine (15 mL) was treated with
anhydrous Ac2O (3.5 mL) and stirred for 6 h. The reaction
mixture was diluted with EtOAc (150 mL), and washed with
10% HCl (3 × 150 mL) and saturated NaHCO3 (100 mL). The
organic layer was dried over anhydrous Na2SO4 and concen-
trated under reduced pressure to give 24 (2.154 g, 94% yield)
as a colorless powder: mp 223-224 °C; [R]D +23.0 (c ) 0.46,
CHCl3); 1H NMR (CDCl3) δ 0.81, 0.82 (6H), 0.95, 1.01 (3H each,
except 0.82, all s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 1.66 (3H,
s; 20-CH3), 2.02, 2.05 (3H each, both s; OCOCH3), 2.42 (1H,
dt, J ) 5.8, 10.8 Hz; H-19), 3.83, 4.23 (1H each, both br d, J )
11.1 Hz; H2-28), 4.45 (1H, dd, J ) 6.1, 10.0 Hz; H-3), 4.57,
4.66 (1H each, both br s; H2-29); EI-MS m/z 526 M+. Anal.
(C34H54O4) C, H.
d, J ) 6.6 Hz; 20-(CH3)2), 0.86 (6H), 0.87, 0.91, 1.05 (3H each,
except 0.86, all s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 1.09 (6H,
s; 3′-CH3, 3′′-CH3), 2.38-2.56 (8H, m; H2-2′, 2′′, 4′, 4′′), 3.86,
4.30 (1H each, both d, J ) 11.0 Hz; H2-28), 4.52 (1H, dd, J )
4.6, 11.0 Hz; H-3). Anal. (C46H76O8) C, H.
3,28-Di-O-(3′,3′-tetr a m eth ylen eglu ta r yl)-d ih yd r obetu -
lin (20): yield 89% (after chromatography with n-hexane/
EtOAc [8:1]), an off-white amorphous powder; [R]25 -18.2 (c
D
1
) 0.52, CHCl3); H NMR (CDCl3) δ 0.78, 0.85 (3H each, both
d, J ) 6.6 Hz; 20-(CH3)2), 0.85, 0.87 (6H), 0.96, 1.05 (3H each,
except 0.87, all s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 2.52-2.63
(8H, m; H2-2′, 2′′, 4′, 4′′), 3.84, 4.28 (1H each, both d, J ) 11.1
Hz; H2-28), 4.51 (1H, dd, J ) 5.4, 10.3 Hz; H-3). Anal.
(C48H76O8‚3/2H2O) C, H.
3,28-Di-O-(-)-ca m p h a n oyl-d ih yd r obetu lin (21): yield
3,28-Di-O-a cetyl-30-br om o-betu lin (25). A mixture of
acetyl ester 24 (2.15 g, 4.08 mmol) and NBS (1.441 g, 8.16
mmol) in CCl4 (82 mL) was stirred for 24 h at room temper-
ature. The precipitate was filtered, and the filtrate was
concentrated and chromatographed over silica gel [hexane/
CH2Cl2 (4:1 f 3:1)]. The product was recrystallized from
hexane to yield a colorless powder, 25 (1.799 g, 73% yield):
mp 185 °C (dec); [R]D +7.4 (c ) 0.49, CHCl3); 1H NMR (CDCl3)
δ 0.81, 0.82 (6H), 0.95, 1.01 (3H each, except 0.82, all s;
4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 2.01, 2.05 (3H each, both s;
OCOCH3), 2.42 (1H, dt, J ) 5.3, 10.8 Hz; H-19), 3.82, 4.24 (1H
each, both br d, J ) 11.1 Hz; H2-28), 3.95 (2H, s; H2-30), 4.44
(1H, dd, J ) 5.5, 10.5 Hz; H-3), 5.00, 5.11 (1H each, both br s;
H2-29); EI-MS m/z 605 [M(81Br)]+, 603 [M(79Br)]+, 524 [M-Br]+.
Anal. (C34H53BrO4) C, H.
3,28-Di-O-a cetyl-30-a cetoxybetu lin (26). A mixture of
bromide 25 (1.696 g, 2.8 mmol), silver acetate (0.935 g, 5.6
mmol), and tetrabutylammonium bromide (180 mg) in anhy-
drous toluene (20 mL) was heated at 70 °C for 12 h. After the
insoluble material was filtered, the solution was concentrated
and chromatographed over silica gel [hexane/CH2Cl2 (3:2)] to
give 26 (1.146 g, 70% yield) as off-white amorphous crystals:
[R]D +7.1 (c ) 0.31, CHCl3); 1H NMR (CDCl3) δ 0.81, 0.82 (6H),
0.95, 1.01 (3H each, except 0.82, all s; 4-(CH3)2, 8-CH3, 10-
CH3, 14-CH3), 2.02, 2.05, 2.08 (3H each, all s; OCOCH3), 2.35
(1H, dt, J ) 5.2, 11.0 Hz; H-19), 3.81, 4.22 (1H each, both br
d, J ) 11.1 Hz; H2-28), 4.44 (1H, dd, J ) 5.7, 10.5 Hz; H-3),
95% (by preparative TLC with n-hexane/EtOAc (4:1)), a white
powder; mp 153-155 °C; [R]25 -9.4 (c ) 0.51, CHCl3); 1H
D
NMR (CDCl3) δ 0.78, 0.86 (3H each, both d, J ) 6.7 Hz; 20-
(CH3)2), 0.88, 0.90 (6H), 0.98 (6H), 0.99, 1.06, 1.07, 1.08, 1.13
(6H) (3H each, except 0.90, 0.98, 1.13, all s; 4-(CH3)2, 8-CH3,
10-CH3, 14-CH3, 6 × CH3 from (S)-camphanoyl), 2.38-2.49
(2H, m; 2 × CH from (S)-camphanoyl), 3.99, 4.42 (1H each,
both d, J ) 11.0 Hz; H2-28), 4.65 (1H, t, J ) 7.9 Hz; H-3). Anal.
(C50H76O8) C, H.
Gen er a l P r oced u r e for Syn th esizin g Betu lin Der iva -
tives (22 a n d 23, 39 a n d 40). A solution of starting material
(0.5 mmol), 4-(dimethylamino)pyridine (1 equiv mol), and an
appropriate anhydride (2 equiv mol) in anhydrous pyridine
(3-5 mL) was heated at 40 °C overnight until the starting
material disappeared on the TLC. The reaction mixture was
diluted with 20 mL of EtOAc and washed with 40 mL of 20%
HCl solution three times. The organic layer was dried over
anhydrous MgSO4 and concentrated under reduced pressure.
The residue was chromatographed using a silica gel column
to afford the product.
28-O-(3′,3′-Dim eth ylglu ta r yl)-betu lin (22): yield 71%
(after chromatography with n-hexane/acetone [4:1]), recovered
betulin 15%, an off-white amorphous powder; [R]25 +12.3 (c
D
) 0.49, CHCl3); 1H NMR (CDCl3) δ 0.77, 0.83, 0.98 (6H), 1.04
(3H each, except 0.98, all s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3),
1.15 (6H, s; 3′-(CH3)2), 1.69 (3H, s; 20-CH3), 2.40-2.48 (5H,